1. Field of the Invention
This invention relates to laminated carpet padding, and methods for its manufacture. More specifically, the laminated structure comprises a layer of rebonded flexible polyurethane foam, a relatively thin intermediate layer of flexible prime polyurethane foam, and a layer of polymer film.
2. Description of Related Art
Laminated structures for use as carpet padding, underlay, or cushioning material are known in the art. U.S. Pat. No. 4,037,013, issued July 19, 1977, discloses a rebonded, or particle, foam bottom layer laminated to a top layer of prime flexible polyurethane foam of equal or greater thickness; and also discloses a laminate of a rebonded foam bottom layer with a top layer of spunbonded polyester fibers, and optionally, intermediate layers of polyethylene film.
U.S. Pat. No. 3,576,706 discloses a laminated carpet underlay of prime, or virgin, flexible polyurethane foam having certain specified physical properties and a facing or cover layer of self-sustaining thermoplastic film 0.5 to 10 mils thick, polyvinyl chloride apparently being preferred. The thermoplastic film facing layer has a relatively low coefficient of friction compared to the flexible foam, and its smooth surface facilitates laying a carpet over the underlay and also helps keep the carpet underlay from wrinkling under the carpet after extended use. In addition to laminating the self-sustaining film, a polyurethane resin facing sheet can be applied by a transfer coating process.
U.S. Pat. No. 4,336,089 discloses a method for simultaneously preparing a polyurethane foam carpet underlay with a barrier film of non-woven material on one surface by applying the film to the upper surface of the curing foam-forming mixture. The film can be polyvinylchloride, polyethylene, polypropylene, copolymers of these materials, nylon, and composites of these materials with non-woven material.
The production of carpet padding from rebonded flexible polyurethane foam is well known. Further, it is well established that carpet padding made of rebonded foam may have on its surface a top, or cover, layer of polymer film, laminated to the rebonded foam through application of heat or a liquid adhesive. The use of rebonded shredded foam is particularly desirable in that it provides an outlet for waste foam generated during production of foam or fabrication of finished items from foam pieces. Because it is usually produced in higher than standard foam densities, rebonded foam padding generally has particularly desirable wear properties. It is, however, also recognized that by its nature rebonded foam is not as uniform in density and surface contour as carpet padding prepared from prime, or virgin, polyurethane foam.
As noted above, the use of a thermoplastic polymer film on the upper surface of the underlay which contacts the back of the carpet is employed to facilitate installation. A cover film frequently used in the manufacture of carpet underlay is polyethylene, although other thermoplastic films can be applied. More recently, the use of a metallized polyester cover film has been adopted. The metallized cover film facilitates the dispersion of static electricity, and with proper grounding, can essentially eliminate the problem. Commercially available metallized polymer films include a 1.25 mm polyethylene (low density) film from Shaw Industries. It is also known to emboss the surface of the film with a repeating pattern, such as diamond-shaped or other geometric indentations. When a cover film is applied to rebonded foam, and particularly when the film's surface is embossed with such a uniform repeating pattern, the nonuniformities of the surface of the underlying rebonded foam become apparent. A cover film applied to rebonded foam generally has a nonuniform appearance, greater variation in cushioning and firmness, and a weaker bond between the film and the foam.